PHASE SHIFTER WITH REDUCED LINEAR DEPENDENCY
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Abstract
A method is disclosed for the automated synthesis of phase shifters—circuits used to remove effects of structural dependencies featured by pseudo-random test pattern generators driving parallel scan chains. Using a concept of duality, the method relates the logical states of linear feedback shift registers (LFSRs) and circuits spacing their inputs to each of the output channels. The method generates a phase shifter network balancing the loads of successive stages of LFSRs and satisfying criteria of reduced linear dependency, channel separation and circuit complexity.
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Citations
49 Claims
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1-35. -35. (canceled)
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36. A built-in-self-test circuit, comprising:
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a linear finite state machine including multiple memory elements with at least one feedback connection between the memory elements, the linear finite state machine having multiple outputs with a substantially balanced load on the outputs; a plurality of scan chains for storing test patterns used to test an integrated circuit; a phase shifter positioned between the linear finite state machine and the scan chains, the phase shifter including a plurality of inputs coupled in parallel to the multiple outputs of the linear finite state machine. - View Dependent Claims (37, 38, 39, 40, 41)
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42. A method for creating a built-in-self-test circuit, comprising:
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generating a linear feedback shift register having multiple flip-flops with outputs of the linear feedback shift register extending from the flip-flops; generating a phase shifter coupled to the linear feedback shift register by randomly selecting the outputs of the linear feedback shift register for coupling to the phase shifter and checking whether the randomly selected outputs will provide adequate interchannel separation that exceeds a predetermined limit and whether loading on the outputs of the linear feedback shift register is substantially evenly distributed; coupling outputs of the phase shifter to a plurality of scan chains for storing test patterns generated by the linear feedback shift register and the phase shifter. - View Dependent Claims (43, 44, 45, 46, 47, 48, 49)
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Specification